Crystal structure, thermal expansion and electrical conductivity of Pr1−xSrxCo0.2Fe0.8O3−δ (0≤x≤0.5)

Perovskite oxides in the system Pr1−xSrxCo0.2Fe0.8O3−δ (0≤x≤0.5) were prepared and characterized. The crystal structure, thermal expansion and electrical conductivity of these oxides were studied by X-ray diffraction, dilatometry and 4-point DC, respectively. The structure of the oxides in the range 0≤x≤0.4 was orthorhombic (Pbnm space group) and became cubic for x=0.5. The lattice parameters were determined. The thermal expansion coefficient (TEC) decreased for x=0.1, and increased for higher x values. The slope of the thermal expansion curves increased and the electrical conductivity decreased at high temperatures, as a result of the loss of lattice oxygen and the formation of oxygen vacancies, a process which is enhanced as the Sr-doping level is increased. The composition Pr0.8Sr0.2Co0.2Fe0.8O3−δ showed the best performance, since its TEC and conductivity values at 700°C (14×10−6 cm (cm °C)−1 and 159 S cm−1, respectively), meet the requirements for application in SOFC cathodes.